Durable flame retardant finish for cellulosic textile materials

ABSTRACT

Flame retardant finishes for cellulosic textile materials containing tetrakis(hydroxymethyl)phosphonium phosphate, tris(hydroxymethyl)phosphine, and at least one organic nitrogenous compound.

United States Patent Stockel et al. 1 Feb. 22, 1972 [54] DURABLE FLAMERETARDANT FINISH [56] References Cited FOR CELLULOSIC TEXTILE NITED TAT5 AT NTS MATERIALS U S E P E 2,809,941 10/1957 Reeves et a1 ..117/136 )1[721 Inventory Rim"! Fm SW91; William 3* 3,236,676 2/1966 Coates et a1...117/137 x Herbs, both of Bndsewafer Townshlp, 2,892,803 1/1959 Reeveset al ..117/136 x Somerset; Sanml James O Brien, Dunel- 3,257,460 6/1966Gordon et a1.... .252/s.1 x 1en,a11ofN.J- 3,013,035 12/1961 Buckler..260/6065 2,911,322 11/1959 Klein et aL... ....117/137 x [73] Ass'gnee'22:? Cymmid 3,452,098 6/1969 VUHO ..260/606.5 [22] Filed: Apr. 9, 1970Primary Examiner-John T. Goolkasian Assistant Examiner-D. J. Fritsch[211 App! 27l67 Attorney-Charles J. Fickey [52] 0.5. CI ..8/1l6.3,8/1162, 117/136, A T C 117/1395 CQ 7/1395 A 252/8'1 Flame retardantfinishes for cellulosic textile materials con- [51 1 Int. Cl. ..D06Ill13/28, D0611] 13/44, C09k 3/28 mi t t ki (hydroxymethyl)phosphoniumphosphate, [58] FlGld ofSearch ..117/136,137,138.5,139.5A,tris(hydroxymethynphosphine and at least one organic 117/1395 CQ;161/191; 252/8.l; 8/116 P, 116.2, 116.3, 116.4; 260/6065 F, 2 P, 29.2;106/15 FP nitrogenous compound.

7 Claims, No Drawings DURABLE FLAME RETARDANT FKNISH FOR CELLULOSICTEXTHJE MATERHALS This invention relates to flame retardant finishes forcellulosic textile materials. More particularly, it relates to aqueousflame retardant finishes containing tetrakis (hydroxymethyl)phosphoniumphosphate, tris(hydroxymethyl)phosphine, and at least one organicnitrogenous compound. It further relates to aqueous solutions containingtetrakis(hydroxymethyl)phosphonium phosphate andtris(hydroxymethyl)phosphine, and to the process for making thesesolutions.

Tetrakis(hydroxymethyl)phosphonium chloride, abbreviated THPC andobtained by reacting 1 mole of tris(hydroxymethyl)phosphine, abbreviatedTHE, 1 mole of formaldehyde and 1 mole of hydrochloric acid, is acomponent of certain flame retardant finishes for textile materials.When applied with organic nitrogenous compounds which contain trivalentnitrogen atoms hearing at least two members of the group consisting ofhydrogen atoms and methylol groups, the treated textile materials haveflame retardant properties which are durable to repeated launderings.The preferred nitrogenous compounds are melamine, urea and water-solublemethylol melamines and methylol ureas. (U.S. Pat. No. 2,809,941 is abasic reference). These finishes provide good flame retardancy which isdurable to laundering, but the finishes impart a stiff and boardy" handand cause an objectionable, and sometimes severe, strength loss of thetreated fabrics. Textile strength, tear strength and abrasion resistanceare reduced.

in U.S. Pat. Nos. 2,892,803 and 3,236,676, it was suggested thattetrakis(hydroxymethyl)phosphonium phosphate of the formula (HOCH PCHOH-H PO '(abbreviated THPP) is the equivalent of THPC in flame retardantfinishes containing nitrogenous compounds. Finishes containing THPPimpart good flame retardancy which is durable to laundering, but againthe treated fabrics are stiff and boardy and suffer from undesirablestrength losses.

In copending, commonly assigned application, Ser. No. 861,481, filedSept. 26, 1969, a flame retardant finish for textile materials isdisclosed comprising an aqueous solution of THP, a methylolatednitrogenous compound and, optionally, urea. Methylolated nitrogenouscompounds include methylolated melamines and methylolated ureas. Thefinish provides flame retardancy only when about three times the usualamount of methylolated nitrogenous compound is used. A very stiff handis obtained.

It is, therefore, an object of this invention to provide a flameretardant finish for cellulosic textile materials which is durable tolaundering.

A further object is to obtain such a finish which imparts a good hand"to the textile material, i.e., it does not make the textile stiff.

Another object is to provide such a finish which is not injurious to thedurability of the fabric to wear.

These and other objects of the invention will become apparent as thedescription thereof proceeds.

It has now been discovered that when an aqueous solution containingtetrakis(hydroxymethyl)phosphonium phosphate,tris(hydroxymethyl)phosphine and at least one organic nitrogenouscompound having trivalent nitrogen bearing at least two members of thegroup consisting of hydrogen atoms and methylol groups, is applied tocellulosic textile materials, the materials become flame retardantwithout appreciable change in the hand or severe strength loss and theflame retardancy is durable to repeated launderings. This is aparticularly surprising discovery in view of the comments above abouteach phosphorus compound when employed separately. Optionally, and oftenpreferably, the flame retardant finish of this invention contains freeformaldehyde.

Aqueous solutions of tetrakis(hydroxymethyl)phosphonium phosphate(THPP), tris(hydroxymethyl)phosphine (TH?) and, optionally, formaldehydecan be prepared by reacting THP with formaldehyde and orthophosphoricacid (H PO in aqueous medium. Sufficient phosphoric acid is used toprovide between 0.15 and 0.60 mole, preferably between 0.25 and 0.4mole, of real orthophosphoric acid per mole of THP. The formaldehydeshould be used in an amount sufficient to provide at least as many molesof formaldehyde as moles of orthophosphoric acid. Preferably at leasttwice as many moles of formaldehyde as orthophosphoric acid should beemployed, i.e., between 0.5 and 1.25 mole of formaldehyde per mole ofTHP. The formaldehyde can be in the form of an aqueous solution or asparaformaldehyde. Sufficient water is present to provide a productsolution with the desired concentration of solids, up to a maximum ofabout 78 percent. When the exothermic reaction subsides, the temperatureof the mixture is held at about 50 C. for about 1 hour.

The product is an aqueous solution which can be used in preparing theflame retardant finishes. The amount of Tl-lPP present in the Prodllcf pnds Oh the amount of" orthophosphoric acid used. Each mole of THPPrequires by theory 1 mole of phosphoric acid and 1 mole of formaldehyde.For each mole of THPP formed, the amount of TH? in the product isreduced by 1 mole. ln actual practice, a little more than 1 mole of TH?per mole of phosphoric acid is converted totetrakis(hydroxymethyl)phosphonium compound.

The nitrogenous compounds of use in this invention include the organicamido compounds which are conventionally employed in the form of theirmethylol derivatives as thermosetting aminoplast textile finishes. Theyinclude the melamines, ureas, cyclic ureas, carbamates, triazinones,etc., and their methylol and alkylated methylol derivatives. Thepreferred nitrogenous compounds are urea, melamine, and water-solublemethylol melamines and methylol ureas. Representative methylol compoundsinclude monomethylol urea, dimethylol urea, tetramethylol urea,dimethylol melamine, partially methylated trimethylol melamine, and thelike. Combinations of two or more nitrogenous compounds may be employed.

The preferred aqueous flame retardant finishes of this invention containurea and methylolated melamine. In preferred embodiments of thisinvention, the aqueous reaction product of 1.0 mole of THP, 0.3 mole oforthophosphoric acid and 1.0 mole of formaldehyde is combined with ureaand a methylolated melamine such as dimethylol melamine or a partiallymethylated trimethylol melamine.

Sufficient flame retardant finish should be applied to the cellulosictextile material to provide between about 1 and 10 percent, preferablybetween about 2 and 4 percent, of phosphine-derived phosphorus based onthe weight of the textile material. The phosphorus from phosphoric acidis disregarded. Sufficient nitrogenous compound is used to providebetween about 3 and 15 percent, preferably between about 5 and 10percent, of nitrogen based on the weight of the textile material. In thecase of the preferred flame retardant finishes, at least 1 percent ofnitrogen is provided by the urea and the methylolated melamine providedbetween about 1 and 10 percent, preferably between about 2.5 and 6percent, of nitrogen, both based on the weight of the textile material.

From these percentages it is a simple matter to calculate the amounts ofphosphorus-containing compounds and nitrogenous compounds to be used inpreparing the flame retardant finishes. Of the totalphosphorus-containing compounds (i.e., THP plus Tl-lPP) between about0.15 and 0.60 mole percent, preferably between 0.25 and 0.40 molepercent, is THPP, and between about 0.85 and 0.40 mole percent,preferably between about 0.75 and 0.60 mole percent, is THP. The ratioof nitrogen of the nitrogenous compounds to phosphine-derived phosphoruson a parts by weight basis is between 15/ l and 3/ 10, preferablybetween 5/1 and 5/4.

The cellulosic textile materials should contain at least 20 percentcellulosic fibers. By cellulosic fibers is meant such fibers as cotton,regenerated cellulose (rayon), linen, jute, etc. Blends of cellulosicfibers or blends of cellulosic fibers with noncellulosic fibers, bothnatural and synthetic, such as silk, wool, nylon, polyester, acrylic,etc., may be used.

obtained an 80 percent wet pickup. The treated fabric, containing 14.5percent solids of the product of Example I (2.0 percentphosphine-derived phosphorus), 7.4 percent of dimethylol melamine (3.75percent melamine-derived or higher. The drying time can range fromseveral minutes at 5 nitrogen) and 4.8 percent of urea (2.24 percenturea-derived the lower temperatures to as low as seconds at the highestr g n), was dried at n h n heated f r L5 temperature. The determiningfactor for time is the reduction minutes at C of the moisture content tosome finite level, e.g., 5-10 per- The durability of the flame retardantfinish to laundering cent. Overdrying is not desirable. The finish iscured at a temwas determlned y repeatedly Washing the fabric in an autoperature between about 125 and 200 C., preferably between 10 maleWashing machine, using water? and a comma" about 150 and 175 c. The timerequired for curing the finish cial detergent. d drying n a tumbledrier- After each 10th is between 5 and 1 minutes, depending on thetemperature Washing and drymg operanon, the flame reslstance of the andthe weight fth textile materiaL fabric was determined by a verticalflame test according to Standard Test Method AATCC 34-l966. The limit ofwash EXAMPLE 1 l5 durability is reached whn the char length is over 6inches. Paraformaldehyde (91 percent real formaldehyde) (133 g.) Theflame retardancy of the treated fabric was durable for was slowly addedto a mixture of 133 g. of 93 percent more than 90 washes. The textilestrength of the fabric (W+F) tris(hydroxymethyl)phosphine, 38 g. of 85percent of was 82 pounds, the warp tear strength was 345 g., the tilltear orthophosphoric acid and 50 g. of water while maintaining astrength was 160 g., the abrasion resistance of .the warp plustemperature of 50 C. When all of the paraformaldehyde was fill was 56percent of that of the untreated fabric, and the hand added, thetemperature was maintained for about 1 hour. The was relativelysoftmolar ratio f n-i (h d h l) h hi /f l. The same fabric treated witha similar finish containing dehyde/phosphoric acid was 1/1/Q,33 Theproduct was an tetrakis(hydroxymethyl)phosphonium chloride instead ofthe aqueous l ti containing 73 percent lid 2 5 product of Example 1 hada flame retardancy also durable for more than 90 washes. However, thetensile stren th of the EXAMPLE e e fabric (W+F) was 67 pounds, the warptear strengt h was 180 Three Preparations A, B and C were made yreacting g., the fill tear strength was 100 g., the abrasion resistanceof together the amounts of y y ynp p warp plus fill was 35 percent ofthat of the untreated fabric, orthophosphorlc acid a Oi aqueous and thehand was stiffer than that of the above treated fabric. dehyde (Cl-I 0)and water shown in Table l. The moles of real reactants are also shown.A m a The pad bath of Example 4 was applied to /65 TABLE I Dacron/cottonfabric by the procedure of Example 4.

35 The flame retardant finish was durable for more than 90 A B C washes.A similar finish containing tetrakis(hydroxmoles g, miss molesymethyl)phosphonium chloride instead of the product of Example l wasdurable for less than 60 washes.

THP(89%) 150 1.075 150 1.075 150 1.075 EXAMPLE6 1-1,1 o, (85%) 41.30.358 62.2 0.538 124.4 1.075 Y C11 0 44% 78.5 1. 78 5 785 Three padbaths were prepared containing the percentage 38 amounts of the productof Example 1 (Prod. Ex. 1), a partially methylated trimethylolmelamine(TMM) and urea shown in Table III. Molar iene erTHP/cH,o/H,Po, 4 TABLE"I A mixture of phosphoric acid and formaldehyde was added in eachpreparation to a mixture of TH? and water while keep- A B C ing thetemperature below about 42 C. by external cooling. Prod. Ex. 1 (solids)15.1% 15.1% 15.1% The mixture was then allowed to slowly cool to about25 C. TMM 73% The product solutions contained 70 percent solids. Urea30% 90% EXAM? 11E 3 The pad baths were applied to cotton sheetingobtaining a Three preparations A, B and C were made by reacting 94percent wet pickup. The treated fabrics A, B and C, contogether theamounts of tris(hydroxymethyl)phosphine 55 taining 14.2 percent solidsof the product of Example 1, 7.3 (THP), aqueous formaldehyde (CH O),orthophosphoric acid percent of partially methylated trimethylolmelamine, and 2.8, (H PO,) and water shown in Table ll. The moles ofreal reacand 4 P respectively, of urea, were dried for 4 tants are alsoshown. W minutes at 107 C. and then heated at 165 C. for 4 minutes.

TABLE II A B C G. Moles G. Moles G. Moles THP (89%) 90 0. 645 90 0.64590 0.645 C1120 (44%) 43.3 0. 645 29.2 0. 430 21. 9 0.323 3P 4 (85%) 24.8 0.215 24.8 0. 215 18.6 0.161 Water 13. 4 17.0 20. 5 Molar ratioill/0.33 1/0. 67/0. 33 1/0. 5/0. 25

*Molar ratio of THP/CH O/HzPOh U V g Wuwwww" i, a. The procedure ofExample 2 was followed. The product The fabrics contained 2.25 percentof phosphine-derived solutions contained 70 percent solids. 7Qphosphorus, 2.35 percent of melamine-derived nitrogen and 3.65, 4.95 and6.25 percent, respectively, of total nitrogen. EXAMPLE 4 The flameretardancy of Fabric A was durable for less than An aqueous pad bath wasprepared containing 18.1 percent 10 washes, of Fabric B and C for atleast 90 washes. The solids of the product of Example 1, 8.7 percent ofurea and 9.3 I treated fabrics hadrelatively soft hands. percent ofdimethylol melamine. The pad bath was applied to A similar finishcontaining tris(hydroxymethyl)phosphine 80 cm. cotton percale by astandard padding procedure (THl) i r 1stead of the product of Example 1provided a flame retardancy durable for less than washes. When theamount of methylolated melamine was tripled, the flame retardancy wasgreatly improved, but the hand of the fabric was stiff.

EXAMPLE 7 A pad bath was prepared containing 21.0 percent solids of theproduct of Example 1, 10.9 percent of partially methy latedtrimethylolmelamine and 8.35 percent of urea. The pad bath was appliedto cotton twill obtaining a 67 percent wet pickup. The treated fabric,containing 14.2 percent solids of the product of Example 1, 7.3 percentof partially methylated trimethylolmelamine and 5.6 percent of urea, wasdried at 107 C. for 4 minutes and then heated at 165 C. for 4 minutes.

The flame retardancy of the treated fabric was durable for more than 90washes. The hand of the fabric was relatively soft;

EXAMPLE 8 Two pad baths A and B were prepared containing 15.0 percentand 18.0 percent solids, respectively, of the product of Example 1, 9.3percent of dimethylolmelamine and 8.7 percent of urea. Pad bath Acontaining 2.50 percent of phosphine-derived phosphorus was applied tocotton broadcloth (Fabric U), cotton flannel (Fabric V), and 80x80cotton per- TABLE IV phosphine-derived Durability Fabric Phosphorus onthe fabric No. of washes U 2.40 25-40 V 2.52 70-80 X-A 2.25 50-70 X-B2.85 I00 Y 309 80-100 Z 3.18 l00 The example demonstrates that the washdurability of the flame retardant finishes of this invention depend notonly on the amount of phosphine-derived phosphorus applied to the fabricbut also on the fiber composition and the construction of the fabric.

EXAMPLE 9 Twelve pad baths were prepared containing sufficient amountsof the products of Examples 2 and 3 to provide 2.5 percent ofphosphine-derived phosphorus in the baths. The baths also containeddimethylolmelamine (DMM) and urea or a partially methylatedtrimethylolmelamine (TMM) and urea. The details are shown in Table V.

TABLE V Percent based on weight of pad bath Pad Bath Prod. of ExampleDMM TMM Urea A 2-A 9.3% 8.7% B 2-A 9.3% 8.7% C 2-B 9.3% 8.7% D 2-B 9.3%8.7% E 2-C 9.3% 8.7%

L 3-C 9 3% K 7;

The pad baths were applied to 2.85 ounces mercerized cotton sheetingobtaining a percent wet pickup. The treated fabrics were dried at 107 C.for 4 minutes and then heated at 165 C. for 4 minutes. The fabricscontained about 2.3 percent phosphine-derived phosphorus.

All of the fabrics possessed an acceptable flame retardancy durable forat least washings.

The hands of the fabrics were examined and the results are shown inTable VI.

' Molar ratio THP/Formaldehyde/Phosphoric Acid This example demonstratesthe advantages of the finishes of this invention, which contain bothTHPP and THP, over finishes containing only THPP (Fabrics E and F). Theexample also demonstrates by Fabrics C and D, that the preferred usageof phosphoric acid is less than 0.5 mole per mole of THP.

When the above procedure was followed using sufficienttetrakis(hydroxymethyl)phosphonium chloride to provide 2.5 percent ofphosphine-derived phosphorus in the pad bath and TMM, the treated fabricdisintegrated after 40 washings.

When the above procedure was followed using sufficienttris(hydroxymethyl)phosphine to provide 2.5 percent of phosphorus in thebaths, there was no flame retardancy when DMM was used, and the flameretardancy was not durable for 10 washes when TMM was used.

We claim:

1. An aqueous flame retardant finish for cellulosic textile materialscomprising tris(hydroxymethyl)phosphine,tetrakis(hydroxymethyl)phosphonium phosphate and at least one organicnitrogenous compound having trivalent nitrogen bearing at least twomembers selected from the group consisting of hydrogen atoms andmethylol groups.

2. The finish of claim 1 wherein the nitrogenous compound is selectedfrom the group consisting of urea, melamine, a water-soluble methylolurea or a water-soluble methylol melamine.

3. The finish of claim 1 wherein the nitrogenous compound is a mixtureof urea and methylolated melamine.

4. The finish of claim 1 where of the total phosphorus-containingcompounds between about 0.15 and 0.60 mole percent istetrakis(hydroxymethyl)phosphonium phosphate and between about 0.85 and0.40 mole percent is tris(hydroxymethyl)phosphine.

5. The finish of claim 1 where the ratio of nitrogen in the nitrogenouscompound to the phosphine-derived phosphorus is between about 15/1 and3/10 on a parts by weight basis.

6. A process of treating cellulosic textile materials to render themflame retardant which comprises applying to said textile the flameretardant finish of claim 1.

7. A textile material obtained by the process of claim 6.

2. The finish of claim 1 wherein the nitrogenous compound is selectedfrom the group consisting of urea, melamine, a water-soluble methylolurea or a water-soluble methylol melamine.
 3. The finish of claim 1wherein the nitrogenous compound is a mixture of urea and methylolatedmelamine.
 4. The finish of claim 1 where of the totalphosphorus-containing compounds between about 0.15 and 0.60 mole percentis tetrakis(hydroxymethyl)phosphonium phosphate and between about 0.85and 0.40 mole percent is tris(hydroxymethyl)phosphine.
 5. The finish ofclaim 1 where the ratio of nitrogen in the nitrogenous compound to thephosphine-derived phosphorus is between about 15/1 and 3/10 on a partsby weight basis.
 6. A process of treating cellulosic textile materialsto render them flame retardant which comprises applying to said textilethe flame retardant finish of claim
 1. 7. A textile material obtained bythe process of claim 6.